Design and Construction Issues for Trenchless Installation of High-Voltage Cable Systems

Trenchless construction methods have been successfully utilized to install numerous types of underground utilities while minimizing disruption to the general public and reducing associated project risks. The planning and design of trenchless construction methods for the installation of high-voltage (up to 345,000-volt) cable systems require unique considerations unlike the installation of water, sanitary, and telecommunication utility installations. Since high-voltage cables are designed to operate at 90°C, pipe temperatures are higher than for other systems. The earth's thermal properties also affect cable rating; and the separation between bores and pipe material selection may be governed by thermal considerations. The maximum installation length may also be limited not by the capabilities of the trenchless construction method selected but governed by the cable shipping lengths. This paper will discuss through actual project case studies the design and construction requirements that are unique to high-voltage electric installations. The paper will also include lessons learned from recent project examples and the factors which contributed to each project's successful use of trenchless methods when installing high-voltage cable systems.